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“Lepiota exudate”

The stems in the specimens at center and the caps in the specimens at left have changed color where the droplets were located before drying.

by Jeff Stallman

On a West Coast road trip in the summer of 2012, California was in the middle of one of its now-famous droughts. In dry Yosemite Valley, I joined a ranger-led walk to hear about the natural history of the area. Enjoying learning about unfamiliar trees and mammals, I was surprised when we happened along a large fruiting of chicken of the woods (Laetiporus sp.). Although the brown grass crinkled beneath our feet and many annual flowers were already deflated by the mid-summer heat, this fungus was fresh and covered with water droplets, nearly to the point where it was dripping on the ground.

This had always impressed me, and I occasionally shared the experience with others as one of those “aren’t fungi interesting and unexpected” stories, but did not think much of it again until years later when hunting in Hawaiʻi.

In Hawaiʻi, an unreported white-spored species in the Agaricaceae is common in wet valleys dominated by alien vegetation.

On the northeastern coast of Hawai’i Island, Waipi’o Valley is one location to commonly find “Lepiota exudate.”

It is mostly plain: normal agaric stature, drab coloration, a cap cuticle which breaks into small squamules, and a simple annulus. What makes the fungus unique are the numerous droplets present on the cap and stem.

The droplets are generally yellow, but orange and red coloration are also found. Even in dry weather, in a hot, often breezy environment, the droplets persist. When they do eventually dry, their former location on the mushroom is obvious due to a discoloration of the stem or cap.

This, along with a citrus smell, makes this “plain” mushroom, quite unique. Work still needs to be done to attribute it to a known species, and until then it’s been nicknamed “Lepiota exudate” in recognition of its most distinguishing feature.

“Lepiota exudate” with yellow water droplets in both young and mature stages as seen in the photos above.

As noted in the article “Why Do Mushrooms Weep,” guttation (the technical term) can be relatively common in developing polypores, corticioid, and stipitate hydnoid (think Hydnellum peckii) fungi, but is uncommon in agarics and boletes, so can be a useful identification feature if it is reliably found. Although the article states that weeping is usually due to standard metabolic processes, it does not make this feature any less intriguing. Guttation makes for unique-looking fungi, fun photographs, and interesting encounters when fungi are able to seemingly create their own moisture in the driest of times.